| Cytochrome P450 1 B1 (CYP1 B1) belongs to the CYP family of enzymes, which are heme-containing monooxygenases. The expression of CYP enzymes within the cardiovascular system plays a crucial role in the modulation of angiogenesis. Mice deficient in CYP1B1 (CYP1B1-/-) exhibit abnormal retinal vascular density and do not respond to ischemia-mediated neovascularization.;To gain further insight into the role CYP1 B1 plays in the endothelium, retinal endothelial cell (EC) were isolated from CYP1B1+/+ and CYP1B1-/- mice. CYP1B1 was constitutively expressed in the retinal EC. CYP1B1-/- retinal EC were less adherent, less migratory, and failed to undergo capillary morphogenesis in Matrigel. Adenovirus expression of CYP1B1 restored capillary morphogenesis of CYP1B1-/- retinal EC. Furthermore, siRNA knockdown of CYP1 B1 diminished the proangiogenic characteristics of CYP1B1+/+ retinal EC. Thus, CYP1B1 expression/activity is essential for proangiogenic properties of retinal EC.;Expression of endothelial nitric oxide synthase (eNOS) and activity are essential during angiogenesis. eNOS levels were dramatically down regulated in the CYP1B1-/retinal EC and retinal vasculature of CYP1B1-/- mice. In addition, restoration of eNOS expression in CYP1B1-/- retinal EC improved migration and capillary morphogenesis of CYP1B1-/- retinal EC. Furthermore, the eNOS level increased upon incubation of CYP1B1+/+ retinal EC with 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a CYP1B1 agonist. Thus, a direct relationship between CYP1 B1 and eNOS expression may exist, such that their coordinated function is essential during angiogenesis.;Expression of the antiangiogenic factor thrombospondin-2 (TSP2) upon increased oxidative stress inhibits capillary morphogenesis of EC. CYP1B1-/- retinal EC expressed high levels of TSP2, which was down-regulated by re-expression of CYP1 B1. We observed increased oxidative stress and sustained activation of transcription factor NF-kappaB in CYP1B1-/- retinal EC. The majority of defects observed in CYP1 B1-/- retinal EC were reversed when the oxygen levels were lowered or an antioxidant added. Increased lipid peroxidation, an indicator of increased oxidative stress, and TSP2 were also observed in retinas from CYP1B1-/- mice, and were reversed by administration of an antioxidant. These findings together suggest that CYP1 B1 metabolizes cell products that modulate intracellular oxidative stress and NF-KB activation, which enhance the release of TSP2 and inhibit angiogenesis. |
